1. Field of the Invention
The present invention relates to a positive resist composition and a compound used in the composition.
Priority is claimed on Japanese Patent Application No. 2004-161983, filed May 31, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of miniaturization. Typically, these techniques for achieving further miniaturization involve shortening of the wavelength of the exposure light source. Until recently, ultraviolet radiation such as g-lines and i-lines had been used as the exposure light source, but nowadays, production using KrF excimer lasers (248 nm) is common, and even ArF excimer lasers (193 nm) are now starting to be introduced.
One example of a known resist material that satisfies the high resolution requirements needed to enable reproduction of a pattern with very minute dimensions is a chemically amplified resist composition, comprising a base resin that displays changed alkali solubility under the action of acid, and an acid generator that generates acid on exposure, dissolved in an organic solvent.
Chemically amplified positive resist compositions that have been proposed as ideal resist materials for exposure using KrF excimer laser lithography typically employ a polyhydroxystyrene-based resin, in which a portion of the hydroxyl groups have been protected with an acid dissociable, dissolution inhibiting group, as the base resin (for example, see patent reference 1).
Examples of the most commonly used acid dissociable, dissolution inhibiting groups include so-called acetal groups, including chain-like ether groups typified by 1-ethoxyethyl groups, and cyclic ether groups typified by tetrahydropyranyl groups, as well as tertiary alkyl groups typified by tert-butyl groups, and tertiary alkoxycarbonyl groups typified by tert-butoxycarbonyl groups.
(Patent Reference 1)
Japanese Unexamined Patent Application, First Publication No. Hei 4-211258
With the recent growing demands for ultra-fine, high resolution resist patterns, improvements in the level of resist pattern defects following developing (surface defects) are becoming increasingly important.
These defects refer to general resist pattern problems and irregularities detected by inspecting the developed resist pattern from directly overhead using a surface defect inspection apparatus, such as that manufactured by KLA Tencor Corporation (brand name “KLA”). Specific examples of these irregularities include post-developing scum (mainly undissolved residues), foam, dust, and bridging between sections of the resist pattern.